Brainstem auditory evoked responses and ophthalmic findings in llamas and alpacas in Eastern Canada

Seventeen llamas and 23 alpacas of various coat and iris colors were evaluated for: (1) deafness by using brainstem auditory evoked response testing; and (2) for ocular abnormalities via complete ophthalmic examination. No animals were deaf. The most common ocular abnormalities noted were iris-to-iris persistent pupillary membranes and incipient cataracts.     

Unilateral and Bilateral Congenital Sensorineural Deafness in Client-Owned Pure-Breed White Cats

Background: Congenital sensorineural deafness has been reported frequently in experimental mixed-breed white cats but there is a paucity of data on occurrence of deafness in client-owned pure-breed white cats.
Objective: To describe hearing status in client-owned pure-breed white cats.
Animals: Eighty-four pure-breed client-owned cats with white coat color of 10 registered breeds presented for routine hearing evaluation before breeding (1995–2008).
Methods: Hearing was assessed by click-evoked brainstem auditory evoked response.
Results: Overall deafness prevalence was 20.2%; 9 cats (10.7%) were bilaterally deaf and 8 cats (9.5%) were unilaterally deaf. There was no association between sex and deafness status ( P = .85). Deafness status was associated with iris color ( P = .04).
Conclusions and Clinical Importance: Congenital sensorineural deafness frequently occurs in pure-breed cats with white coat color. Unilateral sensorineural deafness was as common as bilateral deafness.     

Prevalence of unilateral and bilateral deafness in border collies and association with phenotype

BACKGROUND: Congenital sensorineural deafness (CSD) occurs in Border Collies, but its prevalence and inheritance are unknown. This study estimated the prevalence of CSD in Border Collies and investigated its association with phenotypic attributes linked to the merle gene, including coat pigmentation and iris color. HYPOTHESIS: Deafness in Border Collies is associated with pigmentation patterns linked to the merle gene. ANIMALS: A total of 2597 Border Collies from the United Kingdom. METHODS: A retrospective study of Border Collies tested, during 1994-2002, by using brainstem auditory evoked responses. Associations between deafness and phenotypic attributes were assessed by using generalized logistic regression. RESULTS: The prevalence of CSD in puppies was estimated as 2.8%. The corresponding rates of unilateral and bilateral CSD were 2.3 and 0.5%, respectively. Adjustment for clustering of hearing status by litter reduced the overall prevalence estimate to 1.6%. There was no association between CSD and sex (P = .2). Deaf Border Collies had higher rates of merle coat pigmentation, blue iris pigment, and excess white on the head than normal hearing Border Collies (all P < .001). The odds of deafness were increased by a factor of 14 for Border Collies with deaf dams, relative to the odds for dogs with normal dams (P = .007), after adjustment for phenotypic attributes. CONCLUSIONS AND CLINICAL IMPORTANCE: Associations between CSD and pigmentation patterns linked to the merle gene were demonstrated for Border Collies. Evidence for an inherited component to CSD in Border Collies supports selective breeding from only tested and normal parents to reduce the prevalence of this disease.     

Complex segregation analysis of deafness in Dalmatians

OBJECTIVE: To use pedigree analysis to evaluate the feasibility of a major locus model for deafness in Dalmatians. ANIMALS: 605 purebred Dalmatians from 42 families. PROCEDURE: Hearing loss was evaluated through the brainstem auditory-evoked response. Dogs were classified into mutually exclusive categories: normal hearing, unilaterally deaf, or bilaterally deaf. Information was collected on sex, coat color, presence or absence of a color patch at birth, and eye color. Statistical analyses were performed by use of regressive logistic models designed for complex segregation analysis. Genetic correlations among eye color, deafness, and color patch were estimated. RESULTS: Prevalence of hearing loss was 11% for dogs classified as unilaterally deaf and 5% for dogs that were bilaterally deaf. Complex segregation analysis detected statistical evidence of a single allele with an expected frequency of 0.21 that had an effect on the prevalence of deafness. Results of analyses suggested that this locus cannot completely explain the inheritance and incidence of deafness in Dalmatians. Genetic correlation estimates among deafness, eye color, and color patch revealed strong interrelationships among these characteristics. CONCLUSIONS AND CLINICAL RELEVANCE: To reduce the incidence of hearing loss in Dalmatians, unilaterally deaf, blue-eyed dogs should not be considered as potential parents.     

不同被毛颜色羊驼皮肤组织中成熟黑色素细胞的组织学分析

羊驼是已知家养动物中天然被毛颜色最为丰富的动物之一,本研究旨在在组织水平上观察不同被毛颜色羊驼皮肤组织中成熟黑色素细胞的分布与定位,以揭示羊驼丰富被毛颜色发生的细胞学机制。试验选择白色被毛和有色被毛成年羊驼各1头,盛毛期体侧取样,制备石蜡切片,分别采用多巴染色、甲苯胺蓝染色及多巴—甲苯胺蓝复染,光镜观察、拍照。结果表明,在不同被毛颜色羊驼皮肤组织中均有成熟黑色素细胞的分布,但是分布规律不同,在有色被毛皮肤组织主要分布于毛根成形部,在毛根永久部及表皮也有分布,但是数量较少;白色被毛组织主要分布于表皮,在毛根成形部分布很少,而在真皮部及毛根永久部有少量分布。结果提示:1)羊驼不同被毛颜色发生取决于毛根成形部成熟黑色素细胞的数量;2)从一个侧面佐证了毛囊黑色素细胞与皮肤黑色素细胞在执行功能以及它们所接受的调节信号是不同的。     

Use of brain stem auditory-evoked response to evaluate deafness in a group of Dalmatian dogs

A group of 18 adult and 28 six-week-old purebred Dalmatian dogs was tested for hearing by brain stem auditory-evoked responses. Each ear was tested independently. Absence of a response was considered evidence of deafness in that ear. Responses from bilaterally hearing adults and pups and unilaterally hearing dogs were compared with each other and with responses from normally hearing, adult, mixed-breed dogs. Of the 18 adults tested, 5 had normal responses from both ears, 6 were deaf in both ears, and 7 had a response from only one side. Of 28 pups tested, 14 had normal responses from both ears, 9 had a response from only one ear, and 5 were bilaterally deaf. Wave peak latencies from all ears that responded were within normal limits, except that the 5th and 6th waves from unilaterally hearing adults had significantly longer latencies. There were no differences between males and females.     

A comparison of the brainstem auditory evoked response in healthy ears of unilaterally deaf dogs and bilaterally hearing dogs

Aims

Auditory plasticity in response to unilateral deafness has been reported in various animal species. Subcortical changes occurring in unilaterally deaf young dogs using the brainstem auditory evoked response have not been evaluated yet. The aim of this study was to assess the brainstem auditory evoked response findings in dogs with unilateral hearing loss, and compare them with recordings obtained from healthy dogs.

Methods

Brainstem auditory evoked responses (amplitudes and latencies of waves I, II, III, V, the V/I wave amplitude ratio, wave I-V, I-III and III-V interpeak intervals) were studied retrospectively in forty-six privately owned dogs, which were either unilaterally deaf or had bilateral hearing. The data obtained from the hearing ears in unilaterally deaf dogs were compared to values obtained from their healthy littermates.

Results

Statistically significant differences in the amplitude of wave III and the V/I wave amplitude ratio at 75 dB nHL were found between the group of unilaterally deaf puppies and the control group. The recordings of dogs with single-sided deafness were compared, and the results showed no statistically significant differences in the latencies and amplitudes of the waves between left- (AL) and right-sided (AR) deafness.

Conclusions

The recordings of the brainstem auditory evoked response in canines with unilateral inborn deafness in this study varied compared to recordings from healthy dogs. Future studies looking into electrophysiological assessment of hearing in conjunction with imaging modalities to determine subcortical auditory plasticity and auditory lateralization in unilaterally deaf dogs are warranted.

     

Congenital deafness in Jack Russell terriers: Prevalence and association with phenotype

Congenital hereditary sensorineural deafness is the most common form of deafness in dogs. The objectives of this study were to determine a reliable measure of the prevalence of deafness in Jack Russell terriers, an affected breed, and associations between deafness and phenotypic characteristics. Brainstem auditory evoked response recordings and phenotypic parameters (coat color, coat texture, sex, eye color, sire and dam hearing status) were recorded for 1009 Jack Russell terriers. The prevalence of unilateral and bilateral deafness was 3.57% and 0.50%, respectively, lower by a factor of three to four than in earlier reports based on smaller and closely related kindreds. Significant association with deafness was identified with white coat color and parental hearing status, but not with sex or coat type. Lack of significant sex or coat type associations and the significant association with white coat color are consistent with previous reports. In conclusion the prevalence of deafness in Jack Russell terriers is lower than initially reported. Deafness was associated with white coat color and parental hearing status. The association with parental hearing status supports this form of deafness being a heritable trait in the breed and the association with white coat color supports an inheritance linked to pigmentation genes.     

Does a pleiotropic gene explain deafness and blue irises in white cats?

The prevalence of deafness is high in cat populations in which the dominant white gene is segregating. The objective of this study was to investigate whether there is a gene that is responsible for deafness as well as for blue eyes and to establish a plausible mode of inheritance. For this purpose, data from an experimental colony with deaf cats were analyzed. The hearing status was determined by acoustically evoked brain stem responses (BAER). Complex segregation analyses were conducted to find out the most probable mode of inheritance using maximum likelihood procedures. The prevalence of deafness and partial hearing in the experimental colony was 67% and 29%, respectively. The results of the bivariate segregation analysis support the hypothesis of a pleiotropic major gene segregating for deafness and blue iris colour. The high heritability coefficients for both traits, 0.55 and 0.75 respectively, indicate that beside the major gene there is an important influence of polygenic effects.     

Intraocular pressure in normal llamas (Lama glama) and alpacas (Lama pacos)

Objective: To determine the mean intraocular pressure in llamas ( Lama glama ) and alpacas ( Lama pacos ) using applanation tonometry. Animals studied: Ten llamas and 10 alpacas. Procedures: Intraocular pressure (IOP) was measured with a Tono-Pen™ XL (Mentor Ophthalmics, Inc., Norwell, MA, USA). Three values, with 5% variance, were recorded for each eye. Least-squares means were determined for IOP for each eye of llamas and alpacas. Controlling for age, differences between left and right eye were analyzed using anova . Two age groups were established, less than 5 years and greater than 5 years. The effect of age on IOP within each group was analyzed by linear regression. Probability values of less than 0.05 were considered significant. Results: Comparison of mean IOP between right ( n  = 20) and left eyes ( n  = 20), independent of species type, showed no differences in IOPs for llamas and alpacas. Mean IOP declined with increasing age in llamas and alpacas. Mean IOPs for 20 eyes in 10 llamas was 16.96 ± 3.51 mmHg. Mean IOP for 20 eyes in 10 alpacas was 16.14 ± 3.74 mmHg. Mean IOP for all eyes ( n  = 40), independent of species, was 16.55 ± 3.55 mmHg. The range of IOP in normal llamas and alpacas within 2 SD (95% of the population) was 14.89±18.21 mmHg. Conclusions: There was no significant difference in IOP between alpacas and llamas. Mean IOP in both species decreased with increased age.     

Genotypic characterization of Chilean llama (Lama glama) and alpaca (Vicugna pacos) pestivirus isolates

Llamas and alpacas are domesticated South American camelids (SACs) important to ancestral population in the Altiplano region, and to different communities worldwide where they have been introduced. These ungulates have shown to be susceptible to several livestock viral pathogens such as members of the Pestivirus genus, in particular Bovine Viral Diarrhea (BVDV), but there is little data available on Pestivirus infections in SACs. In this study we aimed to detect and identify Pestivirus genotypes and subgroups infecting SACs in both wild and confined environments. Samples were collected from 136 llamas and 30 alpacas from different areas in the Chilean Altiplano (wild animals), and from 22 llamas and 26 alpacas diagnosed as Pestivirus positive from the Metropolitana region in Chile (confined animals). Seroneutralization tests showed titers lower than 2 in all 166 samples from Chilean Altiplano. These samples were also negative to BVDV isolation, indicating that these animals have not been exposed to Pestivirus. After reactivation of positive samples from the Metropolitana region, the 5′ non-codifying region (5′NCR) and E2 glycoprotein were amplified by RT-PCR from the Pestivirus genome. Viral sequences were pairwise compared and phylogenetic trees were constructed. The 5′NCR analysis showed that all 12 sequenced isolates belonged to BVDV-1. Of particular interest, isolates from eight llama and two alpaca were BVDV-1j and two alpacas were BVDV-1b. In agreement with these results, E2 phylogenetic analysis rendered a similar grouping indicating that all 16 isolates belong to BVDV-1. However, the lower availability of E2 sequences determines the creation of a smaller number of sub-groups than the 5′NCR sequences. Based on the E2 sequences, the 5′NCR BVDV 1j group consisting of all the llamas and 3 alpacas are completely included in the E2 BVDV 1e group. Due to the universal availability of the 5′NCR segment, we propose the classification of these Chilean llamas and alpacas Pestivirus isolates as BVDV 1j and BVDV 1b respectively. Thus, this is the first time BVDV-1j is obtained in SACs. In addition, these results indicate Pestivirus infection in llamas and alpacas is associated with bovine population as genotypes and sub-groups are the same as those affecting Chilean livestock.     

Prevalence of neoplasia in llamas and alpacas (Oregon State University, 2001-2006).

Prevalence and type of neoplastic disease were determined in 551 camelid submissions (368 alpacas [Lama pacos], 180 llamas [Lama glama], and 3 cases in which species was not identified) over a 5-year period. Forty neoplasms were identified in 38 animals (6.9%). Prevalence of neoplasia in llamas was higher (11%) than in alpacas (4.9%). Mean age of camelids with neoplasia was 9.42 +/- 4.9 years. Mean age of alpacas with neoplasia (5.48 +/- 3.7 years) was significantly less than of llamas with neoplasia (12.53 +/- 3.2 years; P < 0.001). Cutaneous and mucocutaneous fibroma/fibropapilloma was most common (10 animals), followed by cutaneous and mucocutaneous squamous cell carcinoma (6 animals), disseminated lymphoma (5 animals), and fibrosarcoma (4 animals). Four of 5 animals with lymphoma were alpacas, aged 0.21 to 4 years. Lymphoma occurred in 1 aged llama (15 years). Disseminated carcinoma and adenocarcinoma occurred in 4 llamas and 2 alpacas, and included biliary (2), gastrointestinal (2), mammary gland (1), and unknown (1) origin. Mean age of camelids with any type of carcinoma or adenocarcinoma (12.36 +/- 2.8 years) was significantly greater than that of camelids with lymphoma (4.24 +/- 6.2 years; P = 0.02). Results indicate that neoplasia is relatively common in camelids and that there are differences between llamas and alpacas as regards prevalence of neoplasia, tumor types, and age at diagnosis.     

Prevalence of Deafness in Dogs Heterozygous or Homozygous for the Merle Allele

Background: Deafness in dogs is frequently associated with the pigment genes piebald and merle. Little is known about the prevalence of deafness in dogs carrying the merle allele.
Objective: To determine the prevalence of deafness in dogs heterozygous and homozygous for the merle allele of the mouse Silver pigment locus homolog (SILV) gene.
Animals: One hundred and fifty-three privately owned merle dogs of different breeds and both sexes.
Methods: Hearing was tested by brainstem auditory-evoked response and classified as bilaterally hearing, unilaterally deaf, or bilaterally deaf. DNA from buccal cells was genotyped as either heterozygous or homozygous for the merle allele. Deafness association tests among merle genotype, eye color, and sex were performed by the χ² test.
Results: Deafness prevalence in merles overall was 4.6% unilaterally deaf and 4.6% bilaterally deaf. There was a significant association between hearing status and heterozygous versus homozygous merle genotype. For single merles ( Mm ), 2.7% were unilaterally deaf and 0.9% were bilaterally deaf. For double merles ( MM ), 10% were unilaterally deaf and 15% were bilaterally deaf. There was no significant association with eye color or sex.
Conclusions: Deafness prevalence in merle dogs was greater than that in some dog breeds homozygous for the piebald gene, such as the English Cocker Spaniel, but comparable to, or lower than, that in the Dalmatian and white Bull Terrier. Dogs homozygous for the merle allele were significantly more likely to be deaf than heterozygotes.     

Diagnosis of deafness in a horse by brainstem auditory evoked potential

Deafness was confirmed in a blue-eyed, 3-year-old, overo paint horse by brainstem auditory evoked potential. Congenital inherited deafness associated with lack of facial pigmentation was suspected. Assessment of hearing should be considered, especially in paint horses, at the time of pre-purchase examination. Brainstem auditory evoked potential assessment is well tolerated and accurate.     

Brainstem Auditory-Evoked Potential Assessment of Congenital Deafness in Dalmatians: Associations With Phenotypic Markers

To screen for congenital deafness, brainstem auditory-evoked potential (BAEP) testing was performed on 1031 Dalmatians from three geographically separated areas. Phenotypic marker assessment was done to determine markers possibly associated with deafness. Markers included sex, hair coat color, pigmentation of different areas of skin (eye rims, nose, and ears), presence of a patch, spot size and marking (density of spotting), sire and dam BAEP status, and presence of iris and retinal tapetal pigmentation. Combined data from all test sites showed 8.1% bilateral deafness (N = 83 dogs) and 21.6% unilateral deafness (N = 223), or an overall 29.7% incidence of hearing disorders. Significant (P less than 0.05) associations with deafness for the data from all test sites combined were seen for patch, sire and dam BAEP, iris pigment, and retinal pigment. However, results differed for several of the significant phenotypic markers when analyses were done on the data from the individual test sites; changes from significant to not significant were found. This suggested the existence of multiple populations of deafness patterns, and reinforced the precautionary conclusion that associations of phenotypic markers with deafness are not necessarily functionally significant.     

Analysis of aqueous humor obtained from normal eyes of llamas and alpacas.

OBJECTIVE: To evaluate composition of aqueous humor obtained from normal eyes of llamas (Lama glama) and alpacas (Lama pacos). SAMPLE POPULATION: Aqueous humor obtained from 10 male llamas and 10 male alpacas. PROCEDURE: All animals had normal eyes, as determined by ocular examination. Aqueous humor samples were obtained via paracentesis of the anterior chamber of animals that were heavily sedated. Chemical analysis included measurement of concentrations of sodium, potassium, magnesium, chloride, bicarbonate, phosphorus, and glucose as well as osmolality and pH. RESULTS: With the exception of potassium concentrations, values for aqueous humor composition did not differ significantly between llamas and alpacas. Mean +/- SD values for llamas and alpacas, respectively, were: sodium, 154.7 +/- 2.1 and 152.7 +/- 2.1 mEq/L; potassium, 5.3 +/- 0.4 and 4.6 +/- 0.4 mEq/L; magnesium, 1.8 +/- 0.1 and 1.7 +/- 0.1 mg/dl; chloride, 130.0 +/- 1.6 and 127.0 +/- 3.3 mEq/L; bicarbonate, 19.2 +/- 1.5 and 20.2 +/- 2.3 mEq/L; phosphorous, 2.7 +/- 0.3 and 2.5 +/- 0.4 mg/dl; glucose, 80.3 +/- 3.9 and 80.8 +/- 7.3 mg/dl; total protein, 29.0 +/- 8.6 and 31.5 +/- 10.1 mg/dl; and osmolality, 305.8 +/- 11.8 and 306.2 +/- 4.9 mOsm. The pH ranged from 7.5 to 8.0 for both species. Potassium concentrations were significantly higher in llamas than alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: Except for potassium, composition of aqueous humor did not differ significantly between llamas and alpacas. Aqueous humor composition of llamas and alpacas is similar to that of other species that have been examined.     

Effects of percutaneous liver biopsy in alpacas and llamas

OBJECTIVE: To determine changes in results of selected serum biochemical tests after a single percutaneous liver biopsy and changes in results of hematologic and selected serum biochemical tests after multiple percutaneous liver biopsies in alpacas and llamas. ANIMALS: 5 llamas and 10 alpacas. PROCEDURE: A single percutaneous liver biopsy was performed in 5 llamas and 6 alpacas. Blood samples were collected before and 1, 2, and 3 days after liver biopsy, and submitted for serum biochemical analysis. In the other 4 alpacas, liver biopsy was performed on day 0 and then weekly for 4 weeks. Blood samples were collected at the time of each biopsy, and CBC and serum biochemical analyses were performed. Attitude and appetite of all animals were evaluated daily. RESULTS: None of the animals developed clinically apparent adverse effects. A mild decrease in sorbitol dehydrogenase activity was detected in animals that underwent a single liver biopsy, and mild decreases in plasma protein and albumin concentrations were detected in animals that underwent multiple biopsies. Other significant changes were not detected. CONCLUSIONS: Results of this study suggest that liver biopsy is safe in healthy llamas and alpacas and that, if necessary, multiple weekly liver biopsies can be performed safely in healthy alpacas.     

N3 potentials in response to high intensity auditory stimuli in animals with suspected cochleo-saccular deafness

We describe a previously un-reported vertex-negative potential evoked by high intensity click auditory stimuli in some dogs and cats with suspected cochleo-saccular deafness. Brainstem auditory evoked potential tracings from 24 unilaterally or bilaterally deaf animals, 22 dogs and 2 cats, among which 21 belonged to breeds with high prevalence of suspected or histologically confirmed cochleo-saccular deafness, were studied retrospectively. Values for latency, amplitude and threshold of this potential in dogs were 2.15+/-0.23 ms, 0.49+/-0.25 microV, and 91.9+/-4.7 dB NHL, respectively (mean+/-SD). Latency and threshold values in cats were in the mean+/-2 SD range of the dog values. Sensitivity to click stimulus polarity and to click stimulus delivery rate pointed towards a neural potential instead of a receptor potential. The vertex-negative wave observed in these animals shares all characteristics with the N3 potential described in some deaf humans with cochlear deafness, where it is presumed to arise from saccular stimulation. The combined degeneration of cochlea and sacculus usually reported in deaf white dogs and cats suggest that N3 may have a different origin in these species.     

Complications after orthopedic surgery in alpacas and llamas: 24 cases (2000-2006)

Objective— To report complications associated with orthopedic surgery in alpacas and llamas.
Study Design— Retrospective study.
Animals— Alpacas (n=18) and llamas (n=6) that orthopedic surgery using internal or external fixation.
Methods— Medical records (January 2000–December 2006) and radiographs were reviewed and owners contacted for follow-up information for alpacas and llamas that had orthopedic surgery involving internal or external fixation. Fourteen camelids had internal fixation, 7 had external fixation, and 3 had a combination of internal and external fixation.
Results— Twenty-two animals (92%) were discharged after surgery (mean hospitalization, 15 days). Of 20 animals with ≥1 year follow-up information, 18 were alive (82%). Postoperative complications related to fracture healing, infection, soft tissue structures, or joints occurred in 21 camelids (87%). Thirteen animals returned to their intended use, 4 animals returned to breeding but not their intended use, 4 were euthanatized, and 3 were only able to be used as pets.
Conclusions— Fixation type (internal, external) did not have any significant effect on complications involving fracture healing, infection, soft tissue structures, or chronic lameness. Camelids with open fractures were more likely to have complications associated with fracture healing, repair, and infection than closed fractures.
Clinical Relevance— Complications after orthopedic surgery in alpacas and llamas are more common than previously reported and may result in chronic lameness or prevent return to their intended use.